Soluble oil



United States Patent O SOLUBLE OIL James L. Jezl, Swarthmore, Pa., assignor to Sun Oil Company, Philadelphia, Pa., a corporation of New Jersey No Drawing. Application November 13, 1952, Serial No. 320,351

2 Claims. (Cl. 252--33.3)

This invention relates to soluble oil compositions comprising mineral oil, alkali metal soaps of carboxylic acids obtained by partial oxidation of mineral oil, and an added organic compound.

It is known in the art to prepare soluble oil compositions emulsifiable in water to form oil-in-Water emulsions by forming a mixture of mineral oil and alkali metal soap of carboxylic acids obtained by partial oxidation of mineral oil. Such compositions may be called for convenience synthetic soluble oils to distinguished them from soluble oil compositions which do not contain soaps of acidic products of oxidation of mineral oil. Major problems involved in the preparation of synthetic soluble oil compositions have been the obtaining of a stable, homogeneous mixture of oil and soap prior to emulsification, and the obtaining of a stable emulsion after. emulsification. The present invention provides a highly stable, homogeneous mixture of oil and soap, and a highly stable emulsion, these effects being obtained by the incorporation in the soluble oil composition of an organic compound as coupling agent or mutual solvent, i. e. solvent for both oil and water. The organic compound employed has a dual function since it both stabilizes the soluble oil prior to emulsification and stablizes the emulsion after emulsification.

The organic compound employed in synthetic soluble oils according to the invention is cyclohexanol. Thus, the soluble oil composition according to the present invention comprises mineral oil, alkali metal soap of carboxylic acids obtained by partial oxidation of mineral oil, and a minor proportion of cyclohexanol. It is generally preferred that the composition should also contain other constituents such as alkali metal petroleum mahogany sulfonates and small amounts of excess alkali metal hydroxide and Water. In some cases, it may be desirable to incorporate alkali metal soap of petroleum naphthenic acids in the soluble oil. Also, in some cases, it may be desirable to incorporate in the soluble oil the entire product of oxidation of mineral oil, rather than just a predominantly corboxylic acid portion thereof.

Preferably the synthetic soluble oils according to the invention contain sulfonates in amount sufficient to provide a sulfonate saponification number equivalent of at least 3. Generally, the sulfonate concentration is not so great as to provide a sulfonate saponification number equivalent greater than 10, more preferably, the sulfonate saponification number equivalent is not greater than 7. The sulfonate saponification number equivalent is determined by measurement, in mg. of KOH per gram, of the saponification number of the sulfonate-containing material prior to mixing with other saponifiable components of the soluble oil, and multiplying the saponification number thus obtained by the weight fraction of the sulfonate-containing material in the compounded soluble oil.

Preferably, the concentration of carboxyl-containing materials in the soluble oils according to the invention is 2 sufficient to provide a carboxylate saponification number equivalent of at least 10, more preferably at least .14. Generally, the content of carboxyl-containing materials is not so great as to provide a carboxylate saponification number equivalent greater than 20, more preferably, the carboxylate saponification number is not greater than 17. The carboxylate saponification number equivalent may be determined in a manner generally similar to that described for determination of sulfonate saponification number equivalents.

The synthetic soluble oils according to the invention are preferably alkaline, having for example free alkalinity Within the range 0.01 to 0.12 percent as NaOH.

The organic compound employed according to the invention as a coupling agent or mutual solvent for synthetic soluble oils may be used if desired in conjunction with other coupling agents or mutual solvents, e. g. monobutyl ether of ethylene glycol.

A preferred range of coupling agent concentration in the soluble oil according to the invention is from 1.25 to 3.0 volume percent. A preferred range of water concentration in the soluble oil is from 2.75 to 5.0 volume percent. Generally, for a given soluble oil there should be at least a certain amount of coupling agent to obtain satisfactory results, but this amount varies for different properties and relative proportions of the other constituents of the soluble oil. Also, there should generally, for satisfactory results, be a watercontent within certain upper and lower limits, but these limits also vary for 'diiferentproperties and relative proportions of the other constituents of the soluble oil.

The mineral lubricating oil employed in the soluble oil composition according to the invention preferably has S. U. viscosity at F. Within the range from 40 to 120.

The mineral oil which is used as oxidation charge, on the other hand, preferably has S. U. viscosity at 100 F. Within the range from to 200. A preferred oxidation charge is petroleum foots oil, but mineral lubricating oils may also be used. Mineral oil, as the term is used in connection with the oxidation charge, is understood to include petroleum wax, preferably paraflin wax having melting point not greater than 100 F., as well as normally liquid oils.

Petroleum foots oil is the oily byproduct obtained in the deoiling of slack wax. When the deoiling is done by sweating, the foots oil is sometimes called sweat oil or sweater oil. When the deoiling is done by filtration of a solution of the slack wax in a solvent for oil, the filtrate obtained is a solution of foots oil in the solvent used, e. g. methyl ethyl ketone or mixtures. thereof with toluene and/or benzene. Petroleum foots oils generally contained substantial amounts of low-melting wax in addition to lubricating oil, the amount of wax depending on the filtration temperature and other variables.

The oxidation charge should have sufticiently low content of aromatic compounds so that there is no substantial inhibition of the oxidation by aromatic com pounds. Therefore, a preferred foots oil charge is one obtained from deoiling of slack wax from a solventrefined lubricating oil, e. g. a furfural-refined lubricating oil.

The oxidized mineral oil employed in the compositions according to the invention can be prepared in any suitable manner. For example, it may be prepared by contacting the heated charge oil in liquid state with a freeoxygen-containing gas, e. g. air, oxygen, ozonized air, etc. The oxidation is preferably conducted under atmospheric pressure or relatively low elevated pressure not exceeding, for example, 100 p. s. i. g. Such operation is advantageous in that the vent gases carry off some of the lowerboiling acidic products, which are undesirable in the soluble oil, and which in operation at higher pressures would remain in the liquid oxidation product. The oxidation is preferably conducted. in the presence of an oxidation catalyst, such as manganese naphthenate, manganese soaps of fatty acids, manganese soaps of carboxylic acids obtained in previous oxidations of mineral oil, etc.

The oxidation is preferably continued at least until the saponification number of the liquid oxidation product is 60, and is terminated before the saponification number of the liquid oxidation product exceeds 120, preferably before the saponification number exceeds 100. Oxidation to too high a saponification number tends to result in formationof oxidation products which have adverse effeet on the soluble oil.

The following examples illustrate the invention:

Example I Synthetic soluble oils were prepared by mixing the following materials in the stated amounts:

Mineral lubricating oil grams 490 Partially oxidized petroleum foots oil do 108 Petroleum naphthenic acids do 140 Petroleum mahogany sulfonates (10.9% solution in mineral oil) grarns 250 Caustic soda, 50 B milliters 17 adjusting the water content of the soluble oil at various levels, and adding cyclohexanol in 2.0 volume percent concentration.

The lubricating oil used had S. U. viscosity at 100 F. of about 100. The naphthenic acids had saponification number of 61. The petroleum sulfonates were sodium soaps of sulfonic acids having saponification number of 13.2, and contained 1.80 weight percent organic $03.

The oxidized foots oil was prepared by partially oxidizing a foots oil obtained in the solvent deoiling of slack wax, the oxidation being performed at 260320 F. and atmospheric pressure by blowing air through the foots oil containing a manganese-naphthenate-containing catalyst. The oxidation was continued until the saponification number of the liquid oxidation product was 78, and 108 grams of that product were then incorporated in the soluble oil.

The naphthenic acids and oxidized foots oil each contributed 8.5 saponification number equivalent to the soluble oils, and the sulfonates contributed 3.3 saponification number equivalent. The compounded soluble oil had free alkalinity of about 0.09-0.10 percent as NaOH.

Each soluble oil composition was tested for stability by allowing it to stand at F. for 48-72 hours and then observing the soluble oil at room temperature to determine whether any oil had separated from the soluble oil to form an upper oil layer, and whether there were any signs of haziness or gelation in the soluble oil. Each soluble oil was rated as stable if there was no discernible oil separation, haziness, or gelation; otherwise, unstable.

Each soluble oil' was also tested for emulsion stability by emulsifying 10 ml. of soluble oil in 90 ml. of added 45 F. tap water having calcium hardness less than 100 p. p. m. as CaCOs, allowing the emulsion to come to room temperature while standing for 24 hours, at the end of which time the appearance of the emulsion was observed, and the emulsion was observed, to determine whether or not it was stable. If the emulsion surface was bright, or if it was only slightly dull, with very little or no cream on the surface, the emulsion was rated stable. If there was a substantial amount of cream or scum or free oil. on the emulsion surface, the emulsion was rated unstable.

The following table shows the results obtained with various water contents and 2.0 volume percent cyclohexanol content:

in the absence of the cyclohexanol, the oil and emulsion are both unstable.

The above table shows that highly satisfactory results are obtained with water contents from 3.0 to 4.0 percent and cyclohexanol contents of 2.0 percent.

Example II Synthetic soluble oils as described in Example 1, containing cyclohexanol as coupling agent, were tested for hard water emulsion stability by emulsifying 10 parts by volume of the soluble oil in parts by volume of 45 F. hard water containing 300 p. p. m. of calcium hardness as CaCOs and p. p. m. of chloride hardness as NaCl, allowing the emulsion to come to room temperature while standing for 24 hours, at the end of which time each emulsion was rated for stability. If the emulsion surface was bright, or if there Was only slight cream or scum on the surface the emulsion was rated stable. If there was heavy cream or scum, or tree oil on the emulsion surface, the emulsion was rated unstable. The tap water emulsions as prepared in the preceding examples are rated somewhat more rigorously than in the hard Water emulsions of the present example, since hard water emulsions generally tend to be less stable than tap water emulsions, and a higher standard must therefore be used for tap water emulsions, in order to provide that in the majority of instances a given soluble oil which gives satisfactory tap water emulsions will also give satisfactory hard water emulsions. The following results were obtained, the oil stabilities having been determined after allowing the soluble oil to stand for one month at 70 F.

Vol. Per- Vol. Percent cent Oil Sta- Emulsion Water Oyclobility Stability hexanol 2. 8 1. 5 Stable.... Stable 2. 8 2. 0 do Do. 3. 2 1. 5 do Do. 3.2 2.0 do Do. 3.6 2. 0 do Do. 4. 0 2.0 do Do.

This example shows that synthetic soluble oils are obtainable containing cyclohexanol as coupling agent in 1.5 to 2.0 percent concentration and having satisfactory emulsion stabilities in hard water emulsions.

Comparison example Synthetic soluble oils were prepared and tested in the same manner disclosed in Example 1 except that in two sets of experiments, l-methyl cyclohexanol and n-hexanol respectively were used as coupling agent in place of cyclohexanol. Each alcohol was tested with various combinations of water content and alcohol content within the ranges 2.0 to 4.0 volume percent water and 0.5 to 2.0 volume percent coupling agent. In no case was a stable emulsion obtained with either l-methyl cyclohexanol or n-hexanol.

The results obtained with l-methyl cyclohexanol indicate the unsuitability of substituted cyclohexanols for use as coupling agents in synthetic soluble oils, as compared with cyclohexanol itself which is highly suitable. The results obtained with n-hexanol indicate the unsuitability of an open-chain hexanol as compared with cyclohexanol.

The properties of the oxidation product which is employed in synthetic soluble oils affect substantially the ease With which oil stability and emulsion stability can be imparted to the soluble oil by use of a coupling agent. The coupling agent according to the invention is particularly advantageous in that it is capable of imparting oil stability and emulsion stability to synthetic soluble oils which contain an oxidation product which makes the soluble oil relatively quite difficult to stabilize.

The invention claimed is:

l. A soluble oil composition comprising: mineral lubricating oil having S. U. viscosity at 100 F. Within the range from 40 to 120 seconds; alkali metal soap of petroleum mahogany sulfonic acids; alkali metal soap of petroleum naphthenic acids; a saponified oxidation product mixture obtained by partially oxidizing petroleum foots oil in liquid phase at a temperature in the range from 260 F. to 320 F. and a pressure from atmospheric to 100 p. s. i. g. in the presence of a metallic oxidation catalyst until the saponification number of the oxidation product mixture is Within the range from 60 to 120 mg. of KOH per gram, and saponifying said oxidation product mixture with an alkali metal basic compound; 2.75 to 5.0 volume percent of Water; and 1.25 to 3.0 volume percent of cyclohexanol; said soluble oil having sulfonate saponification number equivalent within the approximate range from 3 to and carboxylate saponification number equivalent within the approximate range from 10 to 20, approximately half of said carboxylate saponification number equivalent being supplied by said oxidation product mixture.

2. A soluble oil composition comprising: mineral lubricating oil; alkali metal soap of petroleum mahogany sulfonic acids; alkali metal soap of petroleum naphthenic acids; a saponified oxidation product mixture obtained by partially oxidizing petroleum foots oil in liquid phase at a temperature in the range from 260 F. to 320 F. and a pressure from atmospheric to 1100 p. s. i. g. in the presence or" a metallic oxidation catalyst until the saponificat'ion number of the oxidation product mixture is within the range from to mg. of KOH per gram, and saponifying said oxidation product mixture with an alkali metal basic compound; 2.75 to 5.0 volume percent cf water; and 1.25 to 3.0 volume percent of cyclohexanol; said soluble oil having sulfonate saponification number equivalent Within the approximate range from 3 to 10 mg. of KOH per gram and icarboxylate saponification number equivalent Within the approximate range from 10 to 20 mg. of KOH per gram, said saponified oxidation product mixture providing carboxylate saponification number equivalent within the approximate range from 5 to 10 mg. of KOH per gram and said alkali metal soap of petroleum naphthenic acids providing carboxylate saponification number equivalent Within the approximate range from 5 to 10 mg. of KOH per gram.

References Cited in the file of this patent UNITED STATES PATENTS Burwell June 9, 1936 Bjorksten May 24, 1949 OTHER REFERENCES 

1. A SOLUBLE OIL COMPOSITION COMPRISING: MINERAL LUBRICATING OIL HAVING S. U. VISCOSIFY AT 100* F. WITHIN THE RANGE FROM 40 TO 120 SECONDS; ALKALI METAL SOAP OF PETROLEUM MAHOGANY SULFONIC ACIDS; ALL ALI METAL SOAP OF PETROLEUM NAPHTHENIC ACIDS; A SAPONIFIED OXIDATION PRODUCT MIXTURE OBTAINED BY PARTIALLY OXIDIZING PETROLEUM FOOTS OIL IN LIQUID PHASE AT A TEMPERATURE IN THE RANGE FROM 260* F. TO 320* F. AND A PRESSURE FROM ATMOSPHERIC TO 100 P. S. I. G. IN THE PRESENCE OF A METALLIC OXIDATION CATALYST UNTIL THE SAPONIFICATION NUMBER OF THE OXIDATION PRODUCT MIXTURE IS WITHIN THE RANGE FROM 60 TO 120 MG. OF KOH PER GRAM, AND SAPONIFYING SAID OXIDATION PRODUCT MIXTURE WITH AN ALKALI METAL BASIC COMPOUND; 2.75 TO 5.0 VOLUME PERCENT OF WATER; AND 1.25 TO 3.0 VOLUME PERCENT OF CYCLOHEXANOL; SAID SOLUBLE OIL HAVING SULFONATE SAPONIFICATION NUMBER EQUIVALENT WITHIN THE APPROXIMATE RANG FROM 3 TO 10 AND CARBOXYLATE SAPONIFICATION NUMBER EQUIVALENT WITHIN THE APPROXIMATE RANGE FROM 10 TO 20, APPROXIMATELY HALF OF SAID CARBOXYLATE SAPONIFICATION NUMBER EQUIVALENT BEING SUPPLIED BY SAID OXIDATION PRODUCT MIXTURE. 